Question Losing DHCP on router when using bridge mode on bluecurve modem from Shaw

May 18, 2022
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Good morning from Canada! I'm having issues with my internet connection and was hoping for some advice from all of you at Tom's Hardware forums. I have internet with Shaw Cable in Canada. My internet connection is 1GB down and 100Mb up.

I have my Bluecurve modem (model is Arris TG3482ER3) in bridge mode. Directly connected to it is a Unifi USG-3P router running firmware 2.4.8. From their it connects directly to a USW-FLEX-Mini smart switch. From their I have multiple branching devices. Directly connected to first switch is my PC which uses a ethernet cable to plug into the switch. Also on same switch is a second identical switch. On the first switch the second device a UCK-G2-Plus (That is a unifi cloud key gen2) which controls the network and sets up the devices and updates firmware etc. The router has no custom configuration and has dhcp for both WAN and LAN on default. As configured IPV6 is disabled as it requires custom configuration and I had reset router and not done anything beyond set up wifi. I had a sweet custom configuration with separate VLANS for IOT devices etc but turned that all off for ease of testing out this problem.

Randomly the router loses connection to the internet and shows as having no DHCP lease. The internet goes down for about 4 to 5 min at a time. This happens randomly and can happen multiple times a day then not happen for weeks. Its an intermittent problem. The wan interface shows 0.0.0.0 and says no connectivity.

After talking to Shaw they indicated the modem was working and had a good signal. They said there was nothing wrong. The first thing they told me to do was reboot the modem. I had tried that but went through the procedure again with them on the phone. They said the logs they had access to indicated the modem had been running fine for months. I have called back complaining many times with them now telling me to disable bridge mode and use the modem as my primary internet to try and troubleshoot the issue. I have replaced the ethernet cables with new ones bought recently as a further troubleshooting method.

I have tried running Ping plotter which did catch the device when internet stopped working. It showed my ping to google as being about 1500ms and the connection stops somewhere in a google data center and never gets to google.com. At this time the router shows 0.0.0.0 and no IP and no DNS. I assume I lose the lease and it takes modem 5 minutes or so to give me a new one? I have tried doing hard reset on modem and all connected network devices and updating the firmware on devices. I never lose local access to router its only the WAN that goes down. The light for ethernet port on modem and router are lit up just fine so they are talking to each other but no joy! I can ping the router but have no access to modem while it is in bridge mode. The suggestion to just stop using my third party hardware and my problems will go away is sort of really making me mad.

I don't believe the hardware I have is faulty. I could be wrong. I do not have another router to check if issues persists. I originally bought the unifi hardware because the wifi with shaw was crappy and did not even go halfway down my driveway. Now it goes down the road. Also I could not set the router to use google or cloudflare DNS and it was locked to ISP DNS. I'm pretty sure if I disable bridge mode and just use the ISP equipment all of my problems will go away. But I will lose the ability to control DNS unless i configure it device by device. Also I can't set up VLANS or do a bunch of other things I want to do. Any suggestions to intermittent issues with DHCP lease being lost and taking 5 min to get one back for my router would be appreciated.

Upon further inspection I lose my DHCP lease every 1 hour and 10 min. It takes about 5 minutes for the lease to be given to my router. While that is happening the internet is of course down hard.
 
Last edited:

kanewolf

Titan
Moderator
Upon further inspection I lose my DHCP lease every 1 hour and 10 min. It takes about 5 minutes for the lease to be given to my router. While that is happening the internet is of course down hard.
It can make port forwarding difficult, because of the double NAT, but I would recommend you swap back to that config. It may be the only way you get the ISP to continue investigating.
 
May 18, 2022
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I am not using a double nat. I have the modem in bridge mode and have a fully qualified IPV4 address for router. Also the problem appears to be the DHCP lease gets messed up after an hour and fails to renew. I then lose all connectivity when this happens. I lose my IP and it takes 5 minutes for it to be given back.
 

kanewolf

Titan
Moderator
I am not using a double nat. I have the modem in bridge mode and have a fully qualified IPV4 address for router. Also the problem appears to be the DHCP lease gets messed up after an hour and fails to renew. I then lose all connectivity when this happens. I lose my IP and it takes 5 minutes for it to be given back.
Right, my recommendation is to swap back to a double NAT. See if that is stable. It may not be stable either. But at least you did what the ISP asked, you can then go from there.
I don't know if you can see the lease time in the WAN DHCP on a USG 3P. Maybe via the command line. My USG is packed away right not so I can't login and look.
 

Ralston18

Titan
Moderator
This:

"and the connection stops somewhere in a google data center "

That is out of your control and also out of your ISP's control.

Router: I made an attempt to find the router's User Guide/Manual. The objective being to determine if the router 1) has logs for troubleshooting and 2) determine if those logs need to be enabled. If there are logs available and if the logs are enabled then the logs might be helpful.

= = = =

Fall back to as basic a configuration of modem, router, computer and devices as possible. Determine if you can get that configuration to consistently work without problems.

Then start adding devices and/or making required configuration changes. Change only one thing at a time and keep notes accordingly.

Just in case you need to undo some change.

Watch for the loss of DHCP.
 

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